1. Field of the Invention
The present invention generally relates to an apparatus and a method for plating an Nd—Fe—B magnet.
2. Description of the Prior Art
New Nd—Fe—B magnets are considered as third generation rare-earth material since 1983. The Nd—Fe—B magnets are materials that have magnetic properties and include a main phase of Nd2Fe14B and a grain boundary phase of rich neodymium. The Nd—Fe—B magnets also have a poor resistance to corrosion. In addition, the magnetic properties of the Nd—Fe—B magnets can be easily affected by temperature fluctuation. Vacuum evaporation plating method can be used to deposit an anti-corrosion film of metal and/or other functional films on the surface of the Nd—Fe—B magnets. The vacuum evaporation plating method is safe, clean, and provides little damages to the Nd—Fe—B magnets.
Currently methods such as multi-arc ion plating, magnetron sputtering, and multi-arc magnetron sputtering are used to deposit the anti-corrosion film and/or other functional films on the surface of the Nd—Fe—B magnets. However, the methods place large limitations on the target source material because the target source material should be a non-magnetic material. In addition, the methods also have a low the target source material utilization rate which can be very costly when used to plate precious metals.
A metal film can be deposited on the surface of the Nd—Fe—B magnet using the vacuum evaporation plating method. During the vacuum evaporation plating, the utilization rate of the target source material is higher than multi-arc ion plating, magnetron sputtering, and multi-arc magnetron sputtering. However, for target source materials that have high melting points, high temperatures in the vacuum chamber during the vacuum evaporation plating can cause the magnetic materials in the Nd—Fe—B magnets to deteriorate thereby reduces the magnetic properties for the Nd—Fe—B magnets.
Such an apparatus is disclosed in Published Korean Patent Application KR100701267 B1 which discloses a pulse arc generating apparatus. The apparatus includes a furnace defining a vacuum chamber. An anode being elongated is disposed in the vacuum chamber of the furnace. A cathode being elongated is disposed in the vacuum chamber of the furnace and spaced from the anode for plating an Nd—Fe—B magnet. At least one target source holder is disposed in the vacuum chamber, supporting the anode and the cathode in parallel and spaced relationship to one another, and between and spaced apart from the cathode and the anode for receiving a target source material to coat the Nd—Fe—B magnet. A power source is electrically connected to the cathode and the anode for cleaning and vaporizing the target source material and to plate the target source material onto the Nd—Fe—B magnet.
Such a method is disclosed in Published Chinese Patent CN 100582290C. The method includes a step of removing grease from an Nd—Fe—B magnet to produce a purified Nd—Fe—B magnet. The next step of the method is disposing a target source material of metal on at least one target source holder and disposing the purified Nd—Fe—B magnet on a cathode in a vacuum chamber of a furnace opposite of the least one target source holder. After disposing the target source material on the at least one target source holder and the purified Nd—Fe—B magnet on the cathode, the target source material of metal is deposited on the purified Nd—Fe—B magnet to produce a coated Nd—Fe—B magnet.